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Future perfect
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Future perfect continuous
I'll have been ascertaining you'll have been ascertaining she'll have been ascertaining we'll have been ascertaining you'll have been ascertaining they'll have been ascertaining
I'd be ascertaining you'd be ascertaining she'd be ascertaining we'd be ascertaining you'd be ascertaining they'd be ascertaining
Past
I'd have ascertained you'd have ascertained she'd have ascertained we'd have ascertained you'd have ascertained they'd have ascertained
Past continuous
I'd have been ascertaining you'd have been ascertaining she'd have been ascertaining we'd have been ascertaining you'd have been ascertaining they'd have been ascertaining